The present invention relates to a hydraulic control mechanism for an operating element, such as a hydraulic motor, hydraulic cylinder, or the like, with the control mechanism operating with or employing presetting of a set point, for example via a stepping motor, and mechanical indication or feedback of an actual value, whereby valve elements or means regulate the direction and quantity of a pressure medium stream that is supplied to the operating element from a source of pressure medium and that flows back from the operating element to the pressure medium tank.
Various control valve designs are used to build control circuits for controlling hydraulic operating elements. With such control circuits, the presetting of the set point and the feedback of an actual value are frequently effected via rotating components. With the heretofore known apparatus, the difference between the rotating components, which represent the set point and actual values, is converted via mechanical components (worm gears, spindles, toothed racks, etc.) into a linear movement that actuates the actual control valve. Thus, with one known apparatus, this control valve is embodied as a sliding spool, and with another known apparatus, the control valve is comprised of four individually arranged seat valves. Whereas the first mentioned approach makes it possible to have a relatively compact construction of the control valve, the second approach can be realized with only a relatively great outlay for functional components. Furthermore, both approaches have the drawback that mechanical elements are needed for the two-stage conversion of a rotational movement into a linear movement. These mechanical elements necessarily have a certain manufacturing tolerance that by reason of a series connection experiences an undesired summation. In addition, with both approaches additional devices are needed that in the manner of an overload safety device effect an automatic disconnect in the event of a danger of exceeding the control path.
It is an object of the present invention to provide a hydraulic control mechanism of the aforementioned general type that makes it possible to compare the rotational movements of set point and actual values directly with one another, via which a considerably greater precision in a static and dynamic sense can be achieved, which operates as an overload safety device, and which has a considerably more straightforward construction and hence can also be manufactured more economically, all relative to the heretofore known control mechanisms.